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Ecology and Biosphere
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* Study of the interactions of organisms with each other and their environment
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* Biotic-living * Abiotic- non-living BioticAbiotic Biotic Abiotic
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* Population-group of organisms of same species in a specific area * Community- all the populations in an area * Ecosystem- community + abiotic factors * Biome- Major ecosystem that occupies a broad geographic region influenced by climate and characterized by dominant vegetation * Biosphere- all portions of Earth inhabited by life / all of Earth’s ecosystems
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* Determined by… * sunlight, * temperature, * water, * wind, * elevation
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A. Interactions 1. Competition—usually for resources * Niche—organism’s role in its environment ~Can’t have 2 species with the same niche in the same area because of the Competitive Exclusion Principle—2 extremely similar species cannot co-exist in the same place because one will be slightly better at getting the resources and reproduce more. * Resource Partitioning—resources are divided so that species can co-exist and each have it’s own niche
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2. Predation * Animal animal = predator / prey * Animal plant = herbivory 3. Symbiosis * Mutualism (+,+) * Parasitism (+,-) * Commensalism (+, 0)
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B. Trophic Structures * Food web—Messy = Stable
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2. Length of Food Chain in Food Web * Energetic Hypothesis—food chain can’t be long because there is an insufficient transfer of energy (10% Rule) * Dynamic Stability—shorter chains are more stable because disruptions are magnified as you go up (the lower you wipe something out, the more effect it has )
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C. Community Stability 1. Dominant Species—highest in terms of biomass (usually a plant) 2. Keystone Species—not most abundant but most important due to ecological role. If it’s removed from ecosystem there’s a major effect 3. Succession—Predictable sequence of communities that follow each other after a disturbance
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* Succession Terms * Disturbance—what originally “damages” ecosystem * Primary Succession—start with a virtually lifeless area * Secondary Succession—start with some biomass left * Pioneer Species—first species to come into an area * Climax Community—end stage / stable / due to climate
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A. Density: # of organisms/area * Quantitative * 2 lions per mile 2 * Qualitative * The density of lions in my backyard is sparse. B. Distribution: How organisms are arranged/placed * Determined by resources and social behavior
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C.Survivorship: See reading D.Life histories: See reading
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D. Population Growth * Variables: dY = amount of changeN = population size dt = change in timeK = carrying capacity B = number of births r max = maximum per D = number of deaths capita growth rate of population b = per capita birth rate m = per capita death rate Population Growth: dN = B – D OR dN = bN - mN dt
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Density Dependent Factors: Population limiting factors whose effect depends on population density Density Independent Factors: Population limiting factors that are not dependent on population density
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A. Productivity—turning light into sugars 1. Gross Primary Productivity (GPP)—amount of light energy converted to chemical energy in photosynthesis over time 2. Net Primary Productivity— (amount of GPP) – (energy used by plant in cellular respiration [R]) NPP = GPP – R 3. Limits on Production—sun (intensity, depth, penetration); limits on photosynthesis (water); limiting nutrients (N & P)
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Net Annual Primary Production vs. Mean Annual Precipitation
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B. Ecological Pyramids (See Pictures) 1. Production / Energy—amount of energy stored at each level 2. Biomass—amount of biological mass at each level 3. Numbers—number of organisms at each level
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Biomagnification—retained substances become more concentrated as you go up the trophic levels
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C.Greenhouse Effect—Carbon Dioxide (and other gases) allow light through but trap the heat it generates in the atmosphere Global Warming—due to increased carbon dioxide levels, causing increased greenhouse effect
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